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The accidental rainforest

On top of Green Mountain, something strange has been happening. This remote mountain poking into the trade winds from the British imperial outpost of Ascension Island in the mid-Atlantic has created its own fully functioning cloud rainforest ecosystem virtually from scratch in just150 years. It did it from odds and ends of botanical scrap brought in by the Royal Navy. According to ecological theory, rainforests are supposed to evolve slowly over millions of years, as species co-evolve and ecological niches are created and filled. Discovering the Green Mountain cloud forest is like finding that a pile of used car parts in a scrapyard has spontaneously reassembled into a functioning car. Unless, that is, ecologists have gottheirtheories hopelessly wrong.

WHEN Charles Darwin stopped off at the mid-Atlantic island of Ascension in July 1836, homeward bound after his long journey aboard the Beagle, he described an island “entirely destitute of trees”. The near-naked island was no casualty of human activity, however. Eighty years before, when Ascension was still uninhabited except for a few passing sailors, Peter Osbeck, a Swedish priest, dropped by on his way home from China. He wrote of “a heap of ruinous rocks” with a bare, white mountain in the middle.

At about a million years old, the volcanic island was a geological upstart and scarcely able to get going biologically because of its remoteness – some 2000 kilometres from the nearest continent. All it boasted was a couple of dozen species of plant, most of them ferns and some of them found nowhere else.

And so it might have remained. But in 1843, British plant collector Joseph Hooker made …